I made a new logo and lost a lot of time by placing the lights and render the image,moving the lights and render, and moving the light and ....The most difficult thing is to put the lights on the correct place,so the metals looks like metals and the shadows are not to heavy.

Q) Is there a rule or theory how to put the lights and camera for good results ?

It's easy to use too many lights. And it's hard to make metals look like metals. (IMO the "Metal" materials supplied with the program are not especially realistic.) The drawing shown in the attached screenshot uses just three lights: one Headlight, one Ambient light, and one Directional light. Most of the "steel" objects use custom materials with "Wrapped filtered image" Pattern and "Conductor" Reflectance. I always have to use trial and error to find a suitable camera location, rendering in OpenGL or Smooth OpenGL and varying the camera location either with the Examine tool or by dragging with the mouse wheel depressed.